The invention relates to methods and apparatus for making rod-like products of the tobacco processing industry, such as filter rod sections or plain cigars, cigarillos or cigarettes of unit length or multiple unit length.
It is often necessary to form a rod-like filler of tobacco or filter material which contains a fibrous material (such as tobacco or filter tow) and one or more additional materials (such as water in the case of a tobacco filler and a suitable plasticizer in the case of a filler for the making of filter rod sections). Referring to the making of filter rod sections which can be united with plain cigarettes to form filter cigarettes of unit length or multiple unit length, it is customary to contact a running tow of filamentary filter material with a spray of atomized plasticizer (such as triacetin) which bonds spaced-apart portions of filaments in the tow to each other to thus establish a maze of paths for tobacco smoke. It is desirable and advantageous to ascertain the percentage of plasticizer in the tow because this enables the manufacturer to regulate the quantity of plasticizer and to thus determine the resistance which a filter plug offers to the flow of tobacco smoke into the mouth.
Presently known machines for the making of filter rod sections do not embody any means for rapidly, reliably and accurately ascertaining the percentage of plasticizer in the stream of fibrous material which is draped in a web of wrapping material and is converted into filter rod sections of desired (unit or multiple unit) length. One of the reasons for the absence of suitable means for reliably ascertaining the percentage of plasticizer in the filler of a rod which is about to be subdivided into filter rod sections, or the percentage of plasticizer in the filter rod sections, is that the chemical composition of the plasticizer is somewhat related to the composition of the material of the tow and, therefore, presently used monitoring or detecting apparatus cannot adequately and reliably distinguish between the percentages of filter tow material and plasticizer material in the filter rod or in the sections of a filter rod.
Commonly owned U.S. Pat. No. 3,865,016 to Greve discloses a method of producing filter rod sections and of monitoring the quantity of plasticizer in the filler of the filter rod. This patent proposes to remove from the filter rod making machine a certain number of filter rod sections which contain plasticizer and to produce the same number of filter rod sections without any plasticizer therein. The two groups of filter rod sections (with and without plasticizer) are weighed to allow for a determination of the percentage of plasticizer in the respective group of filter rods. In order to produce filter rod sections without plasticizer, it is necessary to temporarily turn off the unit which sprays plasticizer onto the running tow of filamentary filter material, i.e., to interrupt the normal operation of the machine. Thus, each sampling of the percentage of plasticizer in the filter rod sections involves a prolonged interruption of regular operation with attendant huge losses in output. Therefore, such sampling of the percentage of plasticizer is carried out only at infrequent intervals.
Another proposal is disclosed in British Pat. No. 2,120,075 which describes a nuclear magnetic resonance measuring device as a means for ascertaining the percentage of plasticizer in filter rod sections. Such measurement requires a relatively long interval of time during which the article to be tested is immobilized at the testing station. Thus, this proposal also involves an interruption of normal operation of a filter rod making machine and, therefore, its utilization is confined to removal of samples at spaced-apart intervals in order to avoid substantial losses in output which are attributable to a pronounced slowdown during monitoring of a portion of the filter rod or during monitoring of discrete filter rod sections.
Determination of the percentage of plasticizer in a continuous filter rod or in discrete sections of a subdivided filter rod constitutes but one of the tasks which still await an optimum or a highly satisfactory solution in the tobacco processing industry. The situation is somewhat analogous in connection with the determination of moisture content of tobacco in a rod-like filler which is converted into a tobacco rod or into discrete plain cigarettes or other rod-shaped tobacco-containing articles.
Thus, there exists an urgent need for a method and for an apparatus which can be resorted to in order to rapidly, reliably and accurately determine the percentage of different materials in a stream or rod of tobacco or filter material and/or in discrete sections of a tobacco or filter rod without necessitating a prolonged or any slowdown or stoppage of the machine or the production line which turns out such articles. This applies in particular for the measurement of percentages of plasticizer in an unwrapped or wrapped filter rod or in sections of a filter rod as well as for the measurement of moisture content of a draped tobacco filler (e.g., the filler of a cigarette rod which is about to be subdivided into plain cigarettes of unit length) and for the measurement of moisture content of discrete rod-shaped articles which are obtained as a result of subdivision of a draped tobacco filler.